50 years ago the EUROCONTROL Maastricht Upper Area Control Centre began operations, with its four founding States agreeing to jointly provide the air navigation services in their upper airspace. / In those 50 years, MUAC has grown to become the 3rd busiest Centre on the continent, handling in pre-COVID times upwards of 1.9 million flights a year with up to 5,700 flights on peak days. The Centre remains Europe’s only multi-national, civil-military air navigation service provider, providing air traffic control services in the upper airspace of Belgium, Luxembourg, the Netherlands and north-west Germany. (....)